Wire gripper for a drive unit of a wire feeder

ABSTRACT

A gripping device is disclosed for a set of pinch rollers used in a wire feeder that supplies a welding operation with a consumable welding wire. The welding wire passes between the pinch rollers whereby the pinch rollers engage the wire with a gripping force and incrementally rotate to control the outflow of the wire to the welding operation. The gripping device has a first member which is displaceable relative to a second member and a spring mechanism extending between the first and second members which has at least a first and a second spring modulus. The spring mechanism produces the gripping force as the first and the second members are displaced toward one another. The gripper urges one roller of the set of pinch rollers toward the other roller of the set to engage the wire and to apply the gripping force. By including a spring mechanism with a first and second spring modulus, the gripper can apply a first range of gripping forces with the force produced by the first spring modulus and a second range of gripping forces with the force produced by the second spring modulus.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This U.S. patent application is a continuation of pending U.S. patentapplication Ser. No. 11/358,896 filed on Feb. 21, 2006 which is acontinuation of U.S. patent application Ser. No. 10/623,963 filed onJul. 22, 2003, now U.S. Pat. No. 7,026,574.

The present invention relates to wire feeders which feed wire to awelding operation wherein the welding wire must be fed in a controlledmanner without tangling or interruption. Wire feeders are known in theart and are generally shown and described in Seufer U.S. Pat. No.5,816,466 which is hereby incorporated by reference herein as backgroundinformation illustrating the general structure of a wire feederincluding two sets of pinch rollers. Sakai U.S. Pat. No. 5,053,591 isincorporated herein as background information and illustrates theapplication of force on the welding wire by the pinch rollers to gripthe wire. Hubenko U.S. Pat. No. 4,235,362; Gleason U.S. Pat. No.3,694,620; and Okada U.S. Pat. No. 3,730,136 are also incorporated byreference herein as background information further illustrating wirefeeding devices.

TECHNICAL FIELD

This invention relates to the art of dispensing wire and, moreparticularly, to a wire gripper used in a drive unit of a wire feederfor controlling the force which is applied by the pinch rollers againstthe wire driven by the wire feeder.

BACKGROUND OF THE INVENTION

The present invention is particularly applicable for use in connectionwith welding wire feeders and, therefore, the invention will bedescribed with particular reference to wire feeders used in connectionwith a welding operation. However, the invention has broaderapplications and may be used with other types of wire or other wirelikematerials.

It is, of course, well known that utilizing a welding wire as aconsumable electrode in the welding process can enhance the weld.Furthermore, in order to maximize the appearance and strength of theweld, accurately controlling the feed of the welding wire is important.Another important aspect of utilizing a consumable welding wire ismaintaining a consistent and reliable flow of wire to the weldingoperation. As can be appreciated, interruptions in the flow of thewelding wire can stop the welding process thereby reducing itsefficiency.

Another aspect of wire feeding relates to choosing the optimal weldingwire for the particular welding process. In this respect, the type ofmetal to be welded and the desired strength properties of the weldedjoint, will dictate which welding wires should be utilized. As can beappreciated, different welding wires can have very different propertiesboth metallurgically and physically. The primary concern in theinvention of this application relates to the physical properties of thewelding wire. There are several different types of welding wireincluding copper wire, steel wire and aluminum wire. Each of these wireshave different physical characteristics which influence the drive unitof the wire feeder.

One such physical characteristic is the hardness of the wire whichinfluences the pinch rollers ability to grip the wire and accuratelycontrol the feed rate of the welding wire. In view of the importance inmaintaining a desired feed rate, the welding wire feeders known in theart include control systems to accurately control the rotation of thepinch rollers that drive the welding wire. But these control systems areeffective only if the pinch rollers maintain a constant grip on thewire. More particularly, a set of pinch rollers are two opposing rollershaving parallel but spaced roller axes. The rollers rotate in oppositedirections about their respective axis such that the portions of theperipheral roller edges that face one another move in the samedirection. The pinch rollers are moveable toward one another so thewelding wire is sandwiched between both rollers. As the drive unit ofthe wire feeder rotates the set of pinch rollers, the engagement betweenthe pinch rollers and the welding wire drives the wire in the desiredfeed direction. The feed rate of the wire corresponds to the surfacespeed of the peripheral edges of the pinch rollers. As can beappreciated, a wire feeder can include more than one set of pinchrollers as is shown in Seufer and one or all of the sets of pinchrollers can be drive rollers. It should also be appreciated thatnon-drive pinch rollers can be used to help direct the flow of weldingwire.

Turning to roller grip, controlling the outflow of welding wire is afunction of the accuracy of the step motor used to drive the pinchrollers and the slippage between the peripheral edges of the pinchrollers and the welding wire. As can be appreciated, if the pinchrollers move relative to the wire, namely, slide on the surface of thewire, the rotation of the pinch rollers is not fully translated intowire outflow. As a result, prior art welding wire feeders have utilizeddifferent peripheral surfaces on the pinch rollers to maintain accuratecontact with the welding wire. These outer surfaces include knurling oreven high friction materials on the surfaces of the rollers. But it isimportant that the contact between the pinch rollers and the weldingwire does not damage the welding wire which can impact the wire outflowto the welding torch or gun and the welding operation. In addition, itis also advantageous to utilize pinch rollers that have a long servicelife to minimize the repairs necessary to maintain a properlyfunctioning wire feeder.

It has been found that pinch rollers can be used in connection withdifferent types of welding wires. However, the different physicalcharacteristics of the many types of welding wire require differentapplication forces to be applied by the pinch rollers against thewelding wire. More particularly, a soft wire such as a copper wire,requires a low amount of application force to obtain the desired contactbetween the welding wire and the pinch rollers, In contrast, a steelwire requires a much greater application force to prevent slippagebetween the welding wire and the pinch rollers. In fact, the applicationforce necessary to accurately move a steel wire would likely damage acopper wire. Other types of welding wire typically require differentapplication forces. As a result of the different physicalcharacteristics of the many welding wires, prior art feeders are set-upto only work in connection with only a small range of welding wires.Changing from a copper welding wire to a steel welding wire requiresmodifications to the wire feeder that often requires professionalassistance.

A force generating device is used to create an application force that istransferred to the pinch rollers by a force applicator. The forcegenerators can utilize a spring to produce the desired application forcewithin a given range. As the spring is deflected, the application forceincreases. As is known in the art, a spring has a spring modulus orspring rate wherein the spring modulus is the additional force necessaryto deflect the spring an additional unit distance. As an example, acompression spring having a 100 pounds per inch spring modulus will becompressed ½ inch by a 50 pound weight. Similarly, a spring cylinderhaving a spring with a 100 pounds per inch modulus will produce 50pounds of force if the spring is compressed ½ inch. In connection withwire feeders, the 50 pounds force is used to create the applicationforce on the welding wire.

The adjustability of the application force is at least in part afunction of the force generator's ability to controllably compress thecylinder spring. As can be appreciated, based on the spring moduluswhich is linear, controllably compressing the spring will control theapplication force of the pinch rollers. Therefore it is important to beable to accurately control the compression of the spring. As is known inthe art, threaded engagement between two components of the cylinder canbe used to compress the spring and therefore control the applicationforce. The accuracy of this arrangement is influenced by the gauge ofthreads used in the threaded engagement along with the spring modulus.As will be appreciated, a fine thread will provide finer adjustmentability than a coarse thread. Furthermore, a coarse thread will increasethe amount of hand force necessary to compress the spring. But, thecoarse thread will allow quicker changes to the application force.

One of the problems with prior art force generating devices is that easeof use must be compromised to provide increased adjustability to theapplication force. One such compromise is the use of a coarse threads toallowing quicker adjustment to the application forces for differentwelding wires.

Another problem with prior art force generating devices is that majormodifications are necessary in order to obtain the application forcenecessary to work in connection with a wide range of wire types and wiresizes. The basis for the modifications is that force generating springcan produce only a limited range of forces. The range of forces neededto work in connection with both soft and hard wires is great enough tonecessitate an excessively large spring cylinder and a significantamount of adjustment to change the application force from a desiredforce for a soft wire to a desired force for a hard wire. As a result,prior art wire feeders can require professional attention to change fromone type of welding wire to another type of welding wire bynecessitating changes to the force generator cylinder.

Yet another problem with prior art welding wire feeders is that thenecessary adjustability for a soft wire is much different than thenecessary adjustability for a harder wire. In this respect, in order tofine tune the application force for a soft wire, the force generatingdevice must be capable of small incremental changes. More particularly,while a 10 pound change in application force will have a recognizableinfluence on the engagement between the pinch rollers and a soft wire, a10 pound change in a harder wire may have virtually no recognizablechange. Therefore, it is desirable to have finer adjustment abilitiesfor softer wires. But, fine adjustment abilities can be a disadvantagewith harder wires. The fine adjustment can increase the time and effortnecessary to make the adjustment. In view of the fact that the threadsutilized in the generator to compress the cylinder spring cannot beeasily changed, a cylinder designed for fine adjustment of a soft wiremay not even work with a hard wire. Conversely, a cylinder designed tobe used in connection with a hard wire may not have the sensitivitynecessary to make the fine adjustments for use in connection with a softwire. These types of problems necessitate physical changes to the designof the wire feeder to change from a soft wire to a hard wire.

SUMMARY OF THE INVENTION

In accordance with the present invention, provided is a wire gripper foruse in connection with a drive unit of a welding wire feeder whichincludes a force generator that can be effectively used in connectionwith a force applicator for feeding a wide range of welding wire withoutmodification to the physical structure of wire gripper. In this respect,a wire gripper in accordance with the present invention includes a forcegenerator having a cylinder spring with at least two spring moduli. Thetwo spring moduli of the cylinder spring are utilized in differentportions of the stroke of the cylinder to provide at least two ranges ofapplication force and to provide the desired degree of adjustability forthe different ranges of forces.

A wire gripper according to one aspect of the present invention canutilize two separate cylinder springs such that in a first range of thecylinder's stroke, the cylinder engages only one spring to produce afirst range of application force and then in a second range of thestroke, both springs are engaged to produce a second range ofapplication forces. The result is that the spring cylinder according tothe present invention can be compact and can work in connection withmore than one type of welding wire without physical changes.

In accordance with another aspect of the present invention, the firstand second springs can be coaxial to one another.

In accordance with yet another aspect of the present invention, thespring cylinder and springs are all cylindrical and the springs arecompression springs.

In accordance with even another aspect of the invention, the springcylinder can include a spring having more than one spring moduluswherein a single spring will have a different spring modulus atdifferent portions of the cylinder's stroke. In this respect, the springhas a first spring portion with a first spring modulus and at least asecond spring portion having a second spring modulus. In operation, thespring portion with the lesser spring modulus (the first springportion), will deflect first producing a first range of forces.Subsequently, as the first spring portion reaches a set force, thesecond spring portion, with a higher spring modulus, will begin todeflect thereby producing a second range of forces.

In accordance with a further aspect of the invention, the springcylinder can include a spring having a variable rate spring wherein thespring modulus changes throughout the stroke of the cylinder. As can beappreciated, a spring with a variable rate spring modulus results in aspring modulus which constantly changes as the spring is compressed.

The primary object of the present invention is the provision of wiregripper which allows a wire feeder to be used in connection with a widerange of welding wire without significant modification to the wiregripper.

Another object of the present invention is the provision of a wiregripper having a force generator or compression cylinder which allowsthe wire feeder to be used in connection with a wide range of weldingwire without significant modification to the compression cylinder.

Yet another object is the provision of a wire gripper of the foregoingcharacter that provides accurate adjustment to the application force foruse with a wide range of welding wire.

Still another object is the provision of a wire gripper of the foregoingcharacter that provides a wide range of adjustability even though it iscompact in size.

Still yet another object is the provision of a wire gripper of theforegoing character which is easy to adjust for all types of weldingwire.

A further object is the provision of a wire gripper of the foregoingcharacter that can accurately adjust the application force in the pinchrollers for use with a wide range of welding wires.

Yet a further object is the provision of a wire gripper of the foregoingcharacter that can be used in connection with existing welding wirefeeder designs.

Even a further object is the provision of a wire gripper of theforegoing character which utilizes components that are economical tomanufacture, easy to use in the field and have a long service life.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing objects, and others, will in part be obvious and in partbe pointed out more fully hereinafter in connection with a writtendescription of preferred embodiments of the present inventionillustrated in the accompanying drawings in which:

FIG. 1 is a partially sectioned elevational view of a drive unitincluding a wire gripper in accordance with the present invention havinga lever arm, a set of pinch rollers and a compression cylinder;

FIG. 2 is an enlarged sectional view of the compression cylinder shownin FIG. 1 wherein the cylinder is in a first range;

FIG. 3 is an enlarged sectional view of the compression cylinder shownin FIG. 1 wherein the cylinder is in a second range;

FIG. 4 is an exploded view of the compression cylinder shown in FIG. 1;

FIG. 5 is a schematic diagram showing overall spring force versusdeflection;

FIG. 6 is a sectional view of another embodiment of a set of compressionsprings for the compression cylinder shown in FIG. 1;

FIG. 7 is a sectional view of yet another embodiment in which thecompression spring is a single spring having more than one springmodulus; and,

FIG. 8 is a sectional view of even yet another embodiment wherein asingle compression spring is used utilizing a variable rate spring.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now in greater detail to the drawings wherein the showings arefor the purpose of illustrating preferred embodiments of the inventiononly, and not for the purpose of limiting the invention, FIGS. 1-4 showa drive unit 10 for a welding wire feeder (not shown). Drive unit 10includes a support member 12 which is secured to the wire feeder and hasa set of pinch rollers 14 and 16. Pinch rollers 14 and 16 are the driverollers for the drive unit and are connected to an electric drive motorM which is known in the art and schematically shown. As is shown inSeufer, a gear box is used to connect the drive motor to the pinchrollers. It should be appreciated that other drive mechanisms could beused without detracting from the invention of this application.Furthermore, more than one set of drive rollers could also be used inaccordance with the present invention.

Pinch roller 16 is a fixed roller which rotates about a fixed rolleraxle 20 thereby rotating about a fixed roller axis 34. Pinch roller 16is secured to support member 12 such that fixed roller axis 34 isstationary relative to member 12. Conversely, pinch roller 14 is anadjustable roller that is attached to a lever arm 30 by roller axle 22.Pinch roller 14 rotates about a roller axis 32 which can be movedrelative to support member 12 and fixed roller axis 34 which will bediscussed in greater detail below.

The gear mechanism connected between drive motor M and the pinch rollersdrives the rollers such that they rotate in opposite directions relativeto one another. As is shown in FIG. 1, fixed roller 16 rotates clockwisewhile adjustable roller 14 rotates counterclockwise so that peripheraledges 36 and 38 of rollers 14 and 16, respectively, move in a commondirection at contact point 40 with wire 42. As a result, pinch rollers14 and 16 work in connection with one another to drive wire 42 in a feeddirection 44. As can be appreciated, surface speeds of peripheral edges36 and 38 should be the same as the desired wire speed of wire 42 toreduce nicking or other damage to the welding wire. In order to furtherminimize damage to wire 42, drive unit 10 includes wire guides 50 and 52which direct both the inflow and the outflow of the wire through thedrive unit. In this respect, wire guide 50 is the inlet guide for wire42 having an inlet guide hole 54 that is a through hole having adiameter only slightly larger than the largest diameter of welding wireto be used. In similar fashion, wire guide 52 is an outflow guide forthe welding wire having an outlet guide hole 56 sized similar to inletguide hole 54. Inlet and outlet guides 50 and 52, respectively, furtherinclude tapered nose sections 58 and 60, respectively, facing oneanother which allow the wire guides to minimize free wire spaces 64,thereby minimizing the amount of wire which is not guided by the guideholes. As can be appreciated, the drive unit for the welding wire feederis essentially pushing a flexible wire to the welding operation and,therefore, it is important that the flow of the wire is guided toprevent kinking or jamming of the welding wire in the outflow portionsof the wire flow.

The outflow of welding wire is incrementally controlled based on thecontrol of drive motor M. Step motors can be used to quickly start andstop the flow of welding wire as needed by the welding operation. Thecontrols for the drive motor are controlled by the person or machineperforming the welding operation. As can also be appreciated, thecontrol of welding wire can be an important part of the weldingoperation and, therefore, it is important to control the flow of thewelding wire. Slippage between the drive rollers and the welding wirereduces the incremental control of the flow of welding wire and,therefore, it is important to prevent wire slippage without damaging thewelding wire.

An application force between 14 and 16 and wire 42 designated by thearrow 70, influences the likelihood of wire slippage. Application force70 is produced by a wire gripper 80 which includes lever arm 30. Inessence, wire gripper 80 moves adjustable roller 14 relative to fixedroller 16 such that adjustable roller 14 can be moved toward fixedroller 16 to engage welding wire 42 therebetween and can be movedsufficiently away from roller 16 to allow the replacement of the weldingwire or to clear a jam in drive unit 10. This is accomplished by thepivotal engagement between lever arm 30 and support member 12. In thisrespect, lever arm 30 has a pivot end 82 that is pivotally connected tomember 12 at a pivot joint 84. Pivot joint 84 can be any pivot jointknown in the art and is shown as including a pivot mount 86 attached tomember 12 by any known means in the art including welding, bolting ormachining from the drive frame. Pivot mount 86 includes a through hole88 and lever arm 30 includes a through hole 90. A pin 92 passes throughholes 88 and 90 to allow lever arm 30 to freely rotate about lever pivotaxis 94. In order to maintain the pivot pin in the proper position,pivot pin 92 can be press fit into one of the through holes 88 and 90and can be slightly smaller than the other of the through holes 88 and90. The pivot pin can also be a nut and bolt arrangement wherein thepivot pin is threadingly secured in position. As stated above, rolleraxle 32 is secured to lever arm 30 to allow pinch roller 14 to rotaterelative to the lever arm. However, it should be noted that axle 32 canalso be separate from lever arm 30 wherein lever arm 30 merely urgesroller 14 toward roller 16 without detracting from the invention of thisapplication. Roller axle 32 is positioned near the center of lever arm30, but the axle can also be positioned at virtually any point spacedfrom the lever pivot point without detracting from the invention of thisapplication.

Wire gripper 80 further includes a compression cylinder 110. In thisrespect, lever arm 30 has an outer end 100 with a ledge 102 shaped toreceive compression cylinder 110. Ledge 102 is machined from a top edge112 of lever arm 30 and is generally flat. Ledge 102 includes a lockinggroove 114 that works in connection with cylinder 110 to maintaincylinder 110 in a drive position 116 which will be discussed in greaterdetail below. Lever arm 30 further includes an edge ramp 120 at outerend 100 to help facilitate moving cylinder 110 from a released position122 to a drive position 116 which will also be discussed in greaterdetail below. Lever arm 30 has a bottom edge 124 with a clearance notch126 for a compression cylinder mount 130, and a cylinder post slot 132for a cylinder post 134. Both cylinder mount and post 134 will bediscussed in greater detail below.

Compression cylinder 110 is pivotally mounted on support member 12 bycylinder mount 130 which allows cylinder 110 to pivot between releaseposition 122 and drive position 116. Cylinder mount 130 can be connectedto member 12 in similar fashion as lever mount 86. Cylinder mount 130includes a through hole 136 and a pivot pin 138, and cylinder post 134also includes a through hole 140 which receives pivot pin 138 to allowthe pivotal movement of cylinder 110. As stated above, with respect tolever mount 86, any pivotal mount known in the art could be used toallow for the pivotal movement of the compression cylinder.

Post 134 extends into an interior area 146 of cylinder 110 and can beused to hold the cylinder parts together. In greater detail, compressioncylinder 110 includes a fixed slide cylinder 150 and a rotationalcylinder 152 which is displaceable relative to fixed cylinder 150.However, it should be noted that cylinder 110 does not have to becylindrical and that rotational cylinder 152 does not have to rotaterelative to slide cylinder 150. They must merely move relative to oneanother, adjustably, to compress the cylinder spring(s) which will bediscussed below. Slide cylinder 150 includes a base 154 and acylindrical side wall 156 which extend upwardly from base 154 andproduces a cylindrical pocket 158 forming a lower portion of interiorarea 146. While slide cylinder 150 is being described as having acylindrical configuration, other configurations could be also usedwithout detracting from the invention of this application. Cylindricalside wall 156 is coaxial with a cylinder axis 160 and has an outerdiameter 162 transverse to cylinder axis 160. Base 154 includes athrough hole 164 sized to allow the free passage of a lower portion 142of cylinder post 134 relative to fixed cylinder 150. Side wall 156 hasan outer surface 157 with graduations 159 to gauge the adjustment ofcompression cylinder 110. More particularly, as cylinder 152 isdisplaced toward cylinder 150, the bottom edge of cylinder 152 covers aportion of the graduations to indicate the level of adjustment.

Rotational cylinder 152 is also shown and described as beingcylindrical. However, it should also be noted that other configurationscould be used without detracting from the invention of this application.Cylinder 152 is a downwardly open cylinder and is sized slightly largerthan slide cylinder 150 to allow telescoping movement between cylinders150 and 152. Rotational cylinder 152 has a top 170 with cylindrical sidewall 172 extending downwardly from top 170. Side wall 172 is alsocoaxial with cylinder axis 160 and forms a cylindrical pocket 174 openopposite to cylindrical pocket 158 and forming the upper portion ofinterior area 146. Cylindrical pocket 174 has an inside diameter 176which is larger than outside diameter 162 of cylinder 150 to allow fixedcylinder side wall 156 to enter rotating cylinder pocket 174 for thetelescoping movement. Rotational cylinder 152 can also include an outersurface 178 having a non-slip coating and/or an outer texture toincrease the grip between the user's hand and the cylinder to allow theeasy rotation of the cylinder with a minimal hand grip. This can includea rubberized outer surface and/or gripping ribs 178 or other means knownin the art to promote a secure grip. Rotational cylinder 152 furtherincludes an upper threaded opening 190 for threaded engagement with thethreaded upper end of cylinder post 134 which will be discussed ingreater detail below. In order to allow for an increased amount ofadjustment, rotational cylinder 152 includes a threaded extension 192extending downwardly from top 170. By including threaded extension 192,threaded opening 190 can extend well into upper pocket 174 withoutreducing the amount of the pocket which can be used in connection with afirst cylinder spring 200 and second cylinder spring 202 which arediscussed below.

First and second cylinder springs 200 and 202 are compression springs,wherein first compression spring has a first spring modulus and secondcompression spring has a second spring modulus. It should be noted thatwhile compression springs are shown, other types of springs such astension springs or leaf springs could be used without detracting fromthe invention. The first and second spring modulus can be the samemodulus or they can be a different spring modulus. Nonetheless, even ifthe spring moduli are the same, the overall spring modulus will bedifferent depending on whether one or both springs are compressed by thecylinder. In this respect, springs 200 and 202 are positioned in pockets158 and 174 and are captured within the cylindrical pockets. Thisarrangement maintains the relative positions of the compression springsand also reduces the likelihood of contaminants entering into the springmechanism which can affect the performance of the spring mechanism.Springs 200 and 202 extended about post 134. Spring 200 has a free oruncompressed height 204, an outer diameter 206, and an inner diameter208 and is positioned within the cylinder pockets to be essentiallycoaxial with cylinder axis 160. Spring 200 is made from a first diameterspring wire 210. Second spring 202 has a free or uncompressed height220, an outer diameter 222, an inner diameter 224, and is made from asecond diameter spring wire 212 which is smaller than the diameter ofwire 210. Second spring 202 is also essentially coaxial with cylinderaxis 160. In this particular spring arrangement, first spring 200 isboth longer and wider than second spring 202 and has a higher springmodulus. In this respect, height 204 is greater than height 220 andfirst spring inner diameter 208 is larger than second spring outerdiameter 222 to allow second spring 202 to nest within first spring 200and to allow both springs to freely compress based on the relativemovement of rotational cylinder 152 to cylinder 150. Spring 200 has alarger spring modulus since it is made from a large diameter springwire.

Since first spring 200 is longer than second spring 202, first spring200 will be engaged and be compressed by relative displacement ofcylinder 150 toward cylinder 152 before second spring 202 is engaged bycylinder 152. In this respect, rotating cylinder top 170 has a bottomsurface 230 and fixed cylinder base 154 has a top surface 232. Fixedcylinder 150 further includes a lower washer 234 and rotating cylinder152 includes an upper washer 236. Springs 200 and 202 rest on washer234. As rotational cylinder 152 is threaded about an upper threadedportion 240 of post 134, rotational cylinder 152 causes the latter to bedisplaced toward slide cylinder 150. Due to first spring height 204being greater than second spring height 220, upper washer 236 will firstengage spring 200. As cylinder 152 is displaced further toward slidecylinder 150, first spring 200 will be compressed and will produce acylinder spring force based on the compression of only first spring 200.However, as cylinder 152 continues to be rotated and advanced towardslide cylinder 150, upper washer 236 will eventually engage secondspring 202 and begin to compress second spring 202 thereby changing theoverall spring modulus to a function of the spring moduli of both thefirst and second springs.

FIG. 5 is a schematic representation of the changing overall cylinderforce designated by the numeral 250. In this respect, when only thefirst spring 200 is compressed, the increase in overall spring force isshown by segment 260 which is linearly increasing at a fixed rate inrelation to the deflection of the spring. The linear increase is afunction of the spring modulus of spring 200. However, once secondspring 202 is engaged, which is shown as point 260, the overall springforce will increase at a greater rate 264 for the same change indeflection. The linear increase in force in this range of deflection isa function of the spring modulus of spring 200 and the spring modulus ofspring 202. As a result, first spring 200 can be configured for therange of forces needed for a softer wire and can allow for a more finetuned adjustment necessary for the softer wire. In the event that theuser of the wire feeder chooses to change to a harder wire, the grippercan be quickly adjusted so that second spring 202 is engaged therebyproducing the second range of forces at a second level of adjustmentnecessary for the harder wire. Furthermore, the accuracy needed foradjusting the harder wire can be easily obtained without necessitatingmany rotations of cylinder 152.

The cylinder force is transmitted by wire gripper 80 to the pinchrollers 14 and 16 by way of lever arm 30 thereby producing theapplication force. In this respect, at any one adjustment wherein atleast one spring is compressed, rotational cylinder 152 is positionallymaintained relative to frame 12 by cylinder post 134 and cylinder mount130. As a result, slide cylinder 150 is urged downwardly against ledge102 of lever arm 30. This downward movement of slide cylinder 150 movesroller 14 towards fixed roller 16 until the pinch rollers engage wire42. The spring force of the cylinder then provides the necessaryapplication force for the pinch roller. As rotational cylinder 152continues to be advanced toward slide cylinder 150, the force applied tothe end of lever arm 30 is increased thereby increasing the applicationforce between the pinch rollers and the wire.

The spring force produced by spring 200 or springs 200 and 202 alsomaintain cylinder 110 in drive position 116. In this respect, slidecylinder 150 further includes a locking ridge 270 which matingly engageswith locking groove 114. The downward force produced by the spring(s)maintains the locking ridge within the locking groove. As can beappreciated, slide cylinder 150 would have to move upwardly against theforce of the spring(s) to disengage from the locking groove. Thisconnection effectively maintains the compression cylinder in the driveposition while allowing the user to easily disengage the cylinder andmove it to release position 122 if a jam is detected or if new wire isneeded. In order to facilitate the re-engagement of the cylinder in thedrive position, edge ramp 120 guides locking ridge 270 as it moves ontoledge 102 were it can be easily positioned in locking groove 114.Moreover, ramp 120 gradually displaces cylinder 150 relative to cylinder152 to compress the spring(s), if they are engaged, as slide cylinder150 moves toward rotational cylinder 152. Once ridge 270 is orientedover groove 114, the force of the spring(s) will move the ridge intolocking engagement with the groove.

Referring to FIGS. 6-8, t hree additional embodiments are shown. A sstated above, different combinations of springs can be used to obtainthe multiple ranges of adjustment discussed above. The discussion aboveincluded spring 200 having a higher spring modulus than spring 202 andalso being the first spring to be engaged by cylinder 152. Withparticular reference to FIG. 6, springs 280 and 282 are shown whereinspring 280 is the first spring to engage while spring 282 is thesecondary spring. In contrast to springs 200 and 202, the first springto engage, spring 280, has a spring modulus which is less than thespring modulus of second spring 282 to be engaged. This is at least inpart because spring 282 is made from a larger diameter spring wire. Thisspring arrangement provides different ranges of adjustment which are notas closely spaced to one another as the spring arrangement shown withsprings 200 and 202. While springs 200 and 202, and springs 280 and 282are both shown to be nested springs, the springs could be stacked on topof one another. In a stacked spring arrangement, even though bothsprings would be engaged at essentially the same time, the spring withthe smallest spring modulus would deflect first thereby producing thefirst range of application forces. Once the application force reaches alevel great enough to deflect the larger modulus spring, the secondspring would begin to deflect thereby producing the second range ofapplication forces.

Referring to FIG. 7, a spring 290 is shown which has more than onespring modulus. As a result, a single spring can be used to producemultiple ranges of adjustment as discussed above. In this respect, thespring modulus of a compression spring is a function of the materialused to make the spring, the size of the material used, and the numberof turns per unit of length measured. While spring 290 is shown to be acompression spring with a round spring wire 291 having a constant wirediameter throughout the spring, the number of turns per unit of lengthchanges along the length of the spring. As a result, the spring moduluswill vary based on spacing between the turns in the spring. Spring 290can be either multiple modulus spring or a variable modulus springdepending on the spacing of the turns. For example, if a first spacingis used in a first segment of the spring and a second spacing is used onthe remainder of the spring, the spring will essentially have two springmoduli. Spring 290 is shown to be a variable rate spring. Withparticular reference to FIG. 5, segment 292 shows the non-linear orvariable rate nature of spring 290. While spring 290 does not producetwo clear and distinct adjustment ranges, it does allow for the finetuned and precise adjustment needed for the soft wires while stillproviding for the large application force needed for the harder wireswithout requiring significant adjustment of the compression cylinder.

Referring to FIG. 8, a spring 300 is shown which is also a variable ratespring. However, spring 300 utilizes a change in material thickness toachieve the changing spring modulus for the spring. In this respect, thebase 302 of spring 300 has a rectangular cross-sectional configurationwhich is much smaller in area than top 304 which is square. As a result,as spring 300 is compressed, the turns toward the bottom of the springwill more easily compress than the turns at the top of the spring. Thiswill produce the change in spring modulus as is shown by segment 292 inFIG, 5.

It should be appreciated that other combinations of springs could beused to achieve two or more ranges of adjustment for the applicationforce without requiring modification to the wire feeder.

While considerable emphasis has been placed on the preferred embodimentsof the invention illustrated and described herein, it will beappreciated that other embodiments can be made and that many changes canbe made in the preferred embodiment without departing from theprinciples of the invention. Accordingly, it is to be distinctlyunderstood that the foregoing descriptive matter is to be interpretedmerely as illustrative of the invention and not as a limitation.

1. A method of welding with a welding gun and a welding wire feeder,said method comprising: feeding a consumable welding wire into a firstend of a welding wire feeder, through a wire gripping device of saidwelding wire feeder, out of a second end of said welding wire feeder,and into a welding gun; and adjusting a force generator of said wiregripping device of said welding wire feeder from a first force positionbeing within a first soft wire range of adjustable force positions to asecond force position being within a second hard wire range ofadjustable force positions.
 2. The method of claim 1 further comprisingfurther feeding said welding wire through said welding wire feeder andthrough said welding gun by, at least in part, applying a gripping forceto said welding wire corresponding to said second force position.
 3. Themethod of claim 1 further comprising adjusting said force generator ofsaid wire gripping device of said welding wire feeder from said secondforce position being within said second hard wire range of adjustableforce positions to a third force position being within said second hardwire range of adjustable force positions.
 4. The method of claim 3further comprising adjusting said force generator of said wire grippingdevice of said welding wire feeder from said third force position beingwithin said second hard wire range of adjustable force positions to afourth force position being within said first soft wire range ofadjustable force positions.
 5. A method of changing a gripping forceapplied to a wire in a welding wire feeder, said method comprising:adjusting a force generator of a wire gripping device of a welding wirefeeder from applying a first gripping force being within a first softwire range of gripping forces to applying a second gripping force beingwithin a second hard wire range of gripping forces.
 6. The method ofclaim 5 further comprising adjusting said force generator from applyingsaid second gripping force being within said second hard wire range ofgripping forces to applying a third gripping force being within saidsecond hard wire range of gripping forces.
 7. The method of claim 6further comprising adjusting said force generator from applying saidthird gripping force being within said second hard wire range ofgripping forces to applying a fourth gripping force being within saidfirst soft wire range of gripping forces.
 8. A method of changing agripping force on a wire in a welding wire feeder, said methodcomprising: moving a first pinch roller of a wire gripping device towarda second pinch roller of said wire gripping device by applying a forceto a lever arm of said wire gripping device, wherein said applied forcecorresponds to one of two ranges of forces provided by said wiregripping device, and wherein each of said two ranges of forcescorresponds to a different spring modulus provided by said wire grippingdevice.
 9. A method of moving a first pinch roller of a wire grippingdevice of a welding wire feeder toward a second pinch roller of saidwire gripping device, said method comprising: compressing two springswithin said wire gripping device to produce a first wire gripping forcecorresponding to a first soft wire range of adjustable springcompression positions; and further compressing said two springs and alsocompressing two other springs within said wire gripping device toproduce a second wire gripping force corresponding to a second hard wirerange of adjustable spring compression positions.
 10. The method ofclaim 9 further comprising further compressing said two springs and saidtwo other springs to produce a third wire gripping force correspondingto said second hard wire range of adjustable spring compressionpositions.
 11. The method of claim 10 further comprising uncompressingsaid two springs and said two other springs to produce a fourth wiregripping force corresponding to said second hard wire range ofadjustable spring compression positions.
 12. The method of claim 1further comprising: further uncompressing said two springs and said twoother springs; and even further uncompressing said two springs toproduce a fifth wire gripping force corresponding to said first softwire range of adjustable spring compression positions.
 13. The method ofclaim 9 wherein said two springs provide a first spring modulus and saidtwo other springs provide a second spring modulus.
 14. The method ofclaim 9 wherein said two springs provide a first spring modulus and acombination of said two springs and said two other springs provide asecond spring modulus.
 15. The method of claim 9 wherein an uncompressedlength of each of said two springs is greater than an uncompressedlength of each of said two other springs.